The present application relates to a sensor built-in display device in which an electrode, to which a driving signal of sensor detection is applied, is additionally used as an electrode to which a display reference electric potential is applied.
Contact detecting devices that are so-called touch panels are known. The touch panels, that are formed so as to be overlapped with a display panel, allow information input replacing ordinary buttons by displaying various buttons as an image on a display surface. When this technology is applied to small-sized mobile devices, disposition of display and disposition of buttons can be commonly used. Accordingly, a significant advantage of enlarging the screen, saving the space of an operation unit, or a decrease in the number of components is acquired.
As described above, generally a “touch panel” represents a contact detecting device having a panel shape that is built in the display device.
However, when the touch panel is arranged on a liquid crystal panel, the entire thickness of a liquid crystal module is increased. Thus, for example, in Japanese Unexamined Patent Application Publication No. 2008-9750, a liquid crystal display device, to which an electrostatic capacitive-type touch panel is added, having a structure appropriate for decreasing the thickness is proposed.
An electrostatic capacitive-type touch sensor has a plurality of driving electrodes and a plurality of detection electrodes that form electrostatic capacitance together with the plurality of driving electrodes. The detection precision of a sensor is in proportion to the number of the driving electrodes and the detection electrodes. However, in a case where sensor output lines are arranged in addition to the detection electrodes, the number of wirings becomes vast. Accordingly, in order to allow detection electrodes to function as sensor output lines, a driving method in which one of the plurality of driving electrodes is AC driven, and the driving electrode that is AC driven is shifted in a direction (hereinafter, referred to as a scanning direction), in which the driving electrodes are aligned at a constant pitch, becomes a mainstream. In a case where a technique of scanning the driving electrodes that are AC driven in one direction is used, when an electric potential change of the detection electrode is observed in follow-up of the scanning, contact or proximity of a detection target object to the touch panel surface can be detected based on the scanning position in which an electric potential change occurs.